1. Field of the Invention
The invention relates to a control apparatus for a vehicular power transmitting apparatus, and more particularly, to failure detection in that vehicular power transmitting apparatus.
2. Description of the Related Art
Clutches and brakes provided in a vehicular power transmitting apparatus are formed of hydraulic actuators driven by hydraulic pressure, and are controlled appropriately by a hydraulic control circuit. In this hydraulic control circuit there are a plurality of individual linear solenoid valves that are able to be electrically controlled. The apply force of the clutches and brakes is optimally controlled based on control pressure output from these linear solenoid valves. Incidentally, the unit price of such linear solenoid valves is relatively high, so reducing the number of these valves by even one is desirable in view of manufacturing costs. With respect to this, Japanese Patent No. 4069054 describes a hydraulic control apparatus of a power transmitting apparatus in which lockup control of a lockup clutch and control of a forward-reverse switching apparatus are performed using a single linear solenoid valve. Such a structure reduces the number of linear solenoid valves, and thus enables manufacturing costs to be kept down.
Incidentally, Japanese Patent No. 4069054 makes no mention of detecting a failure when some sort of abnormality occurs with the structure that performs both lockup control and clutch control with a single linear solenoid valve described in Japanese Patent No. 4069054. Therefore, with the structure described in Japanese Patent No. 4069054, an oil pressure switch and a hydraulic sensor for detecting a failure of the linear solenoid valve are necessary, and as a result, the hydraulic control circuit becomes complex. In addition, a system is necessary for successively detecting failures in the oil pressure switch and hydraulic sensor themselves, which ends up increasing development man-hours.